The dielectric properties of biological tissue are absolutely fundamental in the understanding of the interaction of electromagnetic (EM) signals with the human body. Tissue dielectric properties are a key element in the assessment of the safety of EM radiation, and the development and refinement of EM imaging and therapeutic medical devices. Highlighting the unquestionable importance of an understanding of biological dielectric measurements, the underlying theoretical principles of dielectric measurements has been investigated for over 100 years and are now well-understood. However, the practical challenges associated with the measurement of the dielectric properties of biological tissue are often greatly underestimated and misconceived. The study of these dielectric properties of human tissue requires a multidisciplinary expertise, spanning physics, clinical biology and engineering, and involves theoretical as well as applied science. These difficult constraints routinely leads to inaccurate dielectric results being reported, or conflicting sets of dielectric measurements being presented to researchers. Since the quality of EM dosimetry studies depend wholly on the accuracy of these dielectric measurements, and the direction of EM medical device development is informed by the same measurements, it leaves European researchers building upon very unsatisfactory and unsteady foundations.
Existing review studies which aimed to provide a solid baseline set of measurements for the dielectric properties of human tissue often simply summarised data from smaller single-tissue studies, involving different measurement methods, varying sample sizes and contrasting measurement environments. Many of these studies also considered sources of errors within these dielectric measurements, but almost always as a secondary concern. In more recent studies, suspected origins of errors in dielectric measurements were listed (both random and systematic) and attempts were made to minimise their effects. However, if this approach were satisfactory, one would reasonably expect there to be relatively good agreement in the results of similar dielectric studies. Unfortunately that has been clearly shown not to be the case in a growing number of recent dielectric studies. These studies have provided a very clear motivation for a thorough and detailed investigation into the often unconsidered factors which influence dielectric measurements, how these factors interact, and how they can be modelled or compensated for to establish the “ground-truth” in terms of dielectric measurement. Moreover, the proposed research programme will seek to bridge the growing disconnect between new dielectric measurements and the underlying theoretical framework. As part of an ambitious high-risk/high-gain proposed research programme, the project will use this new understanding of the dielectric properties of human tissue as a platform for the development of new EM-based medical devices, supporting the economic and societal goals of Horizon 2020.
